Facebook today announced thousands of journalists have enabled Subscribe since September 2011. The average journalist has seen a 320 percent increase in subscribers since November 2011, according to Facebook's analysis.

This is based on a sample of 25 journalists Facebook from across a variety of outlets who enabled Subscribe when it launched. The sample included local, national, and international journalists from various news organizations and primary forms of media. Facebook says the growth is coming from social and interest-based discovery. People discover journalists to subscribe to on Facebook through their friends in the News Feed, Facebook search, Facebook's "people to subscribe to" recommendations engine, and other organic discovery mechanisms (such as simply looking at who your Facebook friends have subscribed to).

Based on Facebook's analysis, here are some of the trends the social network is seeing in the type of content journalists are posting:

Questions and Input: 25 percent of posts contain a question to the reader (either rhetorical or soliciting input/reactions). In an earlier study, Facebook found that posts that sought input received 64 percent more engagement (comments, likes, and shares).

Links: 62 percent of posts contain a link (either to one of the journalist's own stories, or to something else of interest). When reporters include analysis with the links, those links receive 20 percent more referral clicks on average.

Call to Action: 30 percent of posts contain "promotional" language – "read my link," "check out my interview with," and so on. Posts with a call to action receive 37 percent more engagement than an average post.

Photos: 12 percent of posts were photos. Posts with photos receive 50 percent more likes than posts without photos.

Videos: 13 percent of posts are videos (from the scene of reporting, or a behind-the-scenes look at the process of reporting a story).

The following content seems to produce above-average feedback from subscribers:

Commentary and analysis on current events and breaking news receives thrice as many Likes and twice as many shares as the average post. Also, highlighting controversial stories on debatable subject matter can double the number of likes and shares the post receives.

Reader shout-outs can increase in feedback by as much as four times. Also, asking for recommendations can lead to a three time increase in comments above an average post.

In-depth analyses on global issues can yield a 1.5x increase in likes and 2.5x increase in shares.

Powerful photos can yield an increase of a doubling in engagement (Likes, comments and shares). Also, behind-the-scenes photos resulted in up to a four-time increase in engagement (likes, comments, shares).

Humor in posts or a humorous picture can yield a 1.5x increase in likes and almost five time increase in shares. Humor often shows the lighter and more personal side of the journalist, which is likely why it results in higher engagement.

Four months ago, Facebook announced Subscriptions, an optional feature that lets you control what types of stories you get from your friends and non-friends in your News Feed. Subscriptions are meant to help you keep up to date with people you're not friends with.

In other words, these are one-way friendships for subscribing to a public figure, celebrity, politician, journalist, or anyone else who wants to post public updates via their Facebook profile. It benefits both parties: the subscriber (could be you), who wants to use Facebook to receive a person's updates, as well as the public figure (also could be you), who wants to reach their audience on Facebook without having a separate Page. Last month, the company pushed out the Subscribe button to the whole Web, letting you subscribe to a person's content when you're not on Facebook, like a news website, blog, and so on.